1. Field of the Invention
The present invention relates to a diesel engine.
2. Description of Related Art
Conventionally, a flow adjuster for adjusting the flow of intake air or exhaust is provided at the halfway of intake channel or exhaust channel of a diesel engine to throttle the intake flow or the exhaust flow, thereby accelerating warm-up operation in starting engine.
Specifically, when intake flow is throttled by the flow adjuster, the intake air supplied from the outside into the cylinder of the diesel engine and the exhaust discharged from the cylinder is decreased, less heat quantity is lost by the intake-air of which temperature is low as compared to the temperature in the cylinder, and more heat quantity can be given in the cylinder by the exhaust, so that the in-cylinder temperature can be easily raised, thereby accelerating ignition and complete combustion of the fuel.
On the other hand, when the exhaust flow is throttled by the flow adjuster, more high-temperature exhaust can be retained in the cylinder without being discharged and the intake air supplied into the cylinder can be decreased as in throttling the intake air, the inside of the cylinder can be warmed by the temperature of the exhaust and less heat quantity is lost by the intake air, so that in-cylinder temperature can be easily raised and ignition and complete combustion of the fuel can be enhanced.
In the above-described diesel engine, the intake air or exhaust is throttled by the flow adjuster in starting the engine and the throttle of the intake air or the exhaust is released after starting the engine.
However, when no load or small load is applied to the engine after starting the engine where engine speed is high as compared to engine start time, small amount of fuel is supplied into the cylinder on account of small load and combustion time per one time for respective cylinders becomes short on account of high engine speed.
Accordingly, when no or small load is applied to the engine after starting the engine, ignition and complete combustion of fuel are difficult to be caused, and all the cylinders are not ignited, thus causing engine hunching and discharge of non-combusted fuel from the cylinder as white smoke.
Especially, when diesel engine is used as a motor of construction equipment or power generator, diesel engine is often operated in high-idle condition where no load or small load is applied to the engine and engine speed is extremely high. Under such condition, engine hunching and white smoke are likely to be generated.
Further, when a diesel engine is started in cold area or time, since the inside of the cylinder is extremely cold and the temperature of the intake air is substantially low, the possibility of engine hunching and discharge of white smoke are further increased.
Further, in a diesel engine having an intake air charger, the compression ratio is often set smaller than a diesel engine having no intake air charger in order to increase charged air pressure ratio thereof. In this case, the in-cylinder temperature is further difficult to be increased on account of small compression ratio and ignition of fuel and complete combustion are difficult to be occurred. Accordingly, all-cylinder ignition becomes difficult and the possibility of engine hunching and white smoke discharge are further increased.
In recent years, through emulsion fuel composed of mixture of fuel and water has come to be used for decreasing toxic substance in the exhaust such as nitrogen oxide, so-called NOx, of the diesel engine, such emulsion fuel is inferior in selfignition property on account of water. When such difficult-to-be ignited emulsion fuel is used in an engine, fuel ignition and complete combustion become difficult, thereby causing engine hunching and white smoke discharge.
An object of the present invention is to reduce the possibility of engine hunching and to greatly decrease the discharge of white smoke in a diesel engine.
Incidentally, the term of first to ninth predetermined periods are used in the description of the present invention, of which meaning will be easily understood with reference to FIG. 18.
In order to achieve an object of the present invention, a diesel engine according to an aspect of the present invention includes: a combustion stabilization assist for enhancing stabilization of combustion of fuel supplied into a combustion chamber, the combustion stabilization assist being actuated for a predetermined period in accordance with operating condition of the diesel engine, in which the predetermined period is either one of a first predetermined period from starting the diesel engine until the diesel engine reaches a neighborhood of high-idle condition and a second predetermined period from a pre-high-idle step before the condition of the diesel engine reaches the high-idle condition until the condition of the diesel engine reaches the neighborhood of the high-idle condition.
The high-idle condition refers to a situation that the load applied to the engine is low (including zero) and engine speed is high. The pre-high-idle step may be any time after starting the engine and below the high-idle condition.
The neighborhood of high-idle condition refers to a situation that the load applied to the engine is low (including zero) and the engine speed is around the high-idle rotation speed, where the engine speed may approximately coincide with the high-idle rotation speed, may be slightly lower than the high-idle rotation speed, or may be slightly higher than the high-idle rotation speed.
Accordingly to the above arrangement, since the combustion stabilization assist is actuated during either one of the first predetermined period and the second predetermined period, the combustion stabilization assist is actuated at least from the pre-high-idle step until the neighborhood of the high-idle condition of the diesel engine. In other words, since the combustion stabilization assist is actuated during the period where the fuel amount supplied into the combustion chamber is low on account of zero load or low load applied to the diesel engine and fuel combustion time is short on account of high engine speed, the fuel combustion during the period can be enhanced. Accordingly, even when the fuel amount supplied into the combustion chamber is small and combustion time is short, ignition and complete combustion of the fuel can be enhanced, thereby greatly reducing the possibility of engine hunching and white smoke discharge.
Further, when the first predetermined period is used as the predetermined period, the combustion stabilization assist is actuated from the start of the engine. In other words, since the combustion stabilization assist is actuated when the fuel amount supplied into the combustion chamber is small on account of zero or low load applied to the engine and the temperature inside the combustion chamber is low, the ignition and complete combustion of the fuel can be sufficiently enhanced, thereby improving startability of the diesel engine.
A diesel engine according to another aspect of the present invention includes: a combustion stabilization assist for enhancing stabilization of combustion of fuel supplied into a combustion chamber, the combustion stabilization assist being actuated for a predetermined period in accordance with operating condition of the diesel engine, in which the predetermined period is either one of a third predetermined period from starting the diesel engine until a predetermined time has elapsed after the diesel engine reaches a high-idle condition and a fourth predetermined period from a pre-high-idle step before the condition of the diesel engine reaches the high-idle condition until a predetermined time has elapsed after the diesel engine reaches the high-idle condition, and/or either one of a fifth predetermined period from starting the diesel engine until a predetermined load is applied to the engine after the diesel engine reaches the high-idle condition and a sixth predetermined period from a pre-high-idle step before the condition of the diesel engine reaches the high-idle condition until a predetermined load is applied to the engine after the diesel engine reaches the high-idle condition.
According to the above arrangement, since the combustion stabilization assist is actuated during at least one of the periods of the third to the sixth predetermined periods, the combustion stabilization assist is actuated at least from the pre-high-idle step of the diesel engine to the neighborhood of the high-idle condition, so that the ignition and complete combustion of the fuel can be enhanced and the possibility of engine hunching and white smoke discharge can be greatly reduced as in the case of adopting the above first and the second predetermined periods as the predetermined period.
Further, when at least one of the third and the fifth predetermined periods is used as the predetermined period, the combustion stabilization assist is actuated from the start of the engine, so that ignition and complete combustion of the fuel can be sufficiently enhanced as in the case of adopting the first predetermined period as the predetermined period, thereby improving the startability of the diesel engine.
When the third or the fourth predetermined period is adopted as the predetermined period, since the combustion stabilization assist is actuated until a predetermined time is elapsed after the diesel engine reaches the high-idle condition, the combustion stabilization assist can be actuated for a substantially long time. Accordingly, since the diesel engine is sufficiently warmed up, the ignition and complete combustion of the fuel can be sufficiently enhanced and engine hunching and discharge of white smoke can be prevented.
On the other hand, when the fifth or the sixth predetermined period is adopted as the predetermined period, since the combustion stabilization assist is actuated until more than predetermined load is applied to the engine after the diesel engine reaches the high-idle condition, the combustion stabilization assist can be actuated until the engine is substantially warmed by increasing amount of the fuel supplied into the combustion chamber. Accordingly, the diesel engine can be sufficiently warmed up, so that ignition and complete combustion of the fuel can be sufficiently enhanced, thereby preventing engine hunching and discharge of white smoke.
When the combination of the third and the fifth predetermined periods or the combination of the fourth and the sixth predetermined periods are adopted as the predetermined period, the end time of the actuation of the combustion stabilization assist is defined by both of the time and the load applied to the engine. In this case, since the actuation of the combustion stabilization assist is stopped when more than predetermined load is applied to the diesel engine even when the predetermined time has not elapsed after reaching the high-idle condition, the combustion stabilization assist can be immediately stopped when the load is applied immediately after reaching the high-idle condition to increase the fuel amount supplied into the combustion chamber so that the engine is sufficiently warmed requiring no warm-up operation, thereby preventing the temperature of the engine from being excessively raised. On the other hand, since the actuation of the combustion stabilization assist is stopped after a predetermined time is elapsed even when more than predetermined load is not applied after the diesel engine reaches the high-idle condition, the combustion stabilization assist can be immediately stopped when the high-idle condition has continued for a predetermined time and the engine is sufficiently warmed to require no warm-up operation, thereby preventing the temperature of the engine from being excessively raised.
A diesel engine according to still another aspect of the present invention includes a combustion stabilization assist for enhancing stabilization of combustion of fuel supplied into a combustion chamber, the combustion stabilization assist being actuated for a predetermined period in accordance with operating condition of the diesel engine, in which the predetermined period is a seventh predetermined period from before starting the diesel engine until the diesel engine reaches a neighborhood of high-idle condition.
When the seventh predetermined period is adopted as the predetermined period, since the combustion stabilization assist is actuated at least from the pre-high-idle step until the neighborhood of the high-idle condition of the diesel engine, ignition and complete combustion of the fuel can be enhanced and the possibility of engine hunching and discharge of white smoke can be greatly diminished as in the case of adopting the above first and the second predetermined periods as the predetermined period. Further, when the seventh predetermined period is adopted as the predetermined period, the combustion stabilization assist is actuated from the start of the engine, the ignition and complete combustion of the fuel can be sufficiently enhanced, thereby improving startability of the diesel engine as in the case of adopting the first predetermined period as the predetermined period.
Further, when the seventh predetermined period is used as the predetermined period, since the combustion stabilization assist is actuated before starting the engine, the temperature inside the combustion chamber, the intake air etc. can be raised before starting the engine, so that ignition properties and flammability of the fuel can be enhanced from the initial stage of the start of the engine, thereby further improving the startability of the diesel engine.
A diesel engine according to further aspect of the present invention includes a combustion stabilization assist for enhancing stabilization of combustion of fuel supplied into a combustion chamber, the combustion stabilization assist being actuated for a predetermined period in accordance with operating condition of the diesel engine, in which the predetermined period is an eighth predetermined period from before starting the diesel engine until a predetermined time has elapsed after the diesel engine reaches a high-idle condition and/or a ninth predetermined period from before starting the diesel engine until a predetermined load is applied to the engine after the diesel engine reaches the high-idle condition.
When at least one of the eighth and the ninth predetermined periods is used as the predetermined period, the combustion stabilization assist is actuated from the pre-high-idle step until the diesel engine reaches the neighborhood of the high-idle condition, so that ignition and complete combustion of the fuel can be sufficiently enhanced as in the case of adopting the first and the second predetermined periods as the predetermined period, thereby greatly reducing the possibility of engine hunching and discharge of white smoke.
When at least one of the eighth and the ninth predetermined periods is adopted as the predetermined period, since the combustion stabilization assist is actuated from the start of the engine, ignition and complete combustion of the fuel can be sufficiently enhanced as in the case of adopting the first predetermined period as the predetermined period, thereby improving the startability of the diesel engine.
When the eighth predetermined period is adopted as the predetermined period, since the combustion stabilization assist is actuated until a predetermined time is elapsed after the diesel engine reaches the high-idle condition, the diesel engine is sufficiently warmed up as in the case of adopting the third and the fifth predetermined periods as the predetermined period, the ignition and complete combustion of the fuel can be sufficiently enhanced and engine hunching and discharge of white smoke can be prevented.
On the other hand, when the ninth predetermined period is adopted as the predetermined period, since the combustion stabilization assist is actuated until more than predetermined load is applied to the engine after the diesel engine reaches the high-idle condition, the combustion stabilization assist can be actuated until the engine is substantially warmed by increasing the amount of the fuel supplied into the combustion chamber as in the case of adopting the fifth and the sixth predetermined periods as the predetermined period. Accordingly, the diesel engine can be sufficiently warmed up, so that ignition and complete combustion of the fuel can be sufficiently enhanced, thereby preventing engine hunching and discharge of white smoke.
When the combination of the eighth and the ninth predetermined periods is adopted as the predetermined period, the end time of the actuation of the combustion stabilization assist is defined by both of the time and the load applied to the engine. Accordingly, the combustion stabilization assist can be immediately stopped when no warm-up operation becomes required as in the case of adopting the combination of the third and the combination of the fifth predetermined periods and the fourth and the sixth predetermined periods, thereby preventing the temperature of the engine from being excessively raised.
When one of the eighth and the ninth predetermined periods is adopted as the predetermined period, since the actuation of the combustion stabilization assist is actuated before starting the engine, the temperature inside the cylinder or the temperature of the intake air can be raised before starting the engine as in the case of adopting the seventh predetermined period as the predetermined period, so that the ignition properties and flammability of the fuel can be enhanced from the initial stage of starting the engine, thus further improving the startability of the diesel engine.
In the above arrangements of the diesel engine, the combustion stabilization assist may preferably include a flow adjuster provided at the halfway of an intake channel or an exhaust channel of the diesel engine for adjusting a flow of an intake air or an exhaust flowing through the channels and a flow adjustment controller for controlling the operation of the flow adjuster.
According to the above arrangement, since the operation of the flow adjuster is controlled so that the flow of the intake air or the exhaust is throttled during the predetermined periods, much exhaust can be reserved inside the combustion chamber and the amount of the intake air supplied into the combustion chamber can be reduced. Accordingly, even when the amount of the fuel supplied into the combustion chamber is small, the heat quantity taken away by the intake air of which temperature is normally low as compared to the temperature inside the combustion chamber and the heat quantity given to the inside of the combustion chamber by the exhaust can be increased, so that the temperature inside the combustion chamber can be easily raised and ignition and complete combustion of the fuel can be enhanced.
When the combustion stabilization assist including the flow adjuster and the flow adjustment controller is used, the pre-high-idle step of the high-idle condition may preferably be set when a rotation speed of the engine becomes an approximately middle-rotation speed between a low-idle rotation speed and high-idle rotation speed of the diesel engine.
When the rotation speed of the diesel engine is higher than the engine rotation speed approximately in the middle of the speed during low-idle condition and the speed during the high-idle condition, the exhaust flow from the engine is increased and exhaust speed gets higher. By throttling the exhaust during the period when the exhaust speed is high, impurities such as carbon in the exhaust is flowed being urged by the exhaust to be unlikely to be caught in the flow adjuster, cleaning efficiency around the flow adjuster can be reduced.
In the above-arranged diesel engine, a combustion stabilization assist may preferably include an intake heater for heating the intake air of the diesel engine.
According to the above arrangement, since the warmed intake air can be supplied into the combustion chamber, the combustion chamber can be warmed by the intake air, so that ignition and complete combustion of the fuel can be enhanced.
Alternatively, the combustion stabilization assist may preferably include: a temperature adjuster for adjusting the temperature of the diesel engine by circulating a thermal medium; a thermal medium heater for heating the thermal medium of the temperature adjuster; a flow-path opener/shutter for opening and shutting a flow-path of the thermal medium of the temperature adjuster; and a flow-path open/shut controller for controlling the operation of the flow-path opener/shutter so that the flow-path of the thermal medium is opened during the predetermined period.
According to the above arrangement, since the operation of the flow-path opener/shutter is controlled by the flow-path open/shut controller during the predetermined period so that the flow-path of the thermal medium is opened, the thermal medium heated by the thermal medium heater is circulated to warm the diesel engine. Accordingly, the combustion chamber and the intake air etc. supplied to the combustion chamber can be warmed, so that ignition and complete combustion of the fuel can be enhanced.
When the combustion stabilization assist includes the temperature adjuster, the thermal medium heater, the flow-path opener/shutter and the flow-path open/shut controller, the flow-path open/shut controller may preferably control the operation of the flow-path opener/shutter so that the flow-path of the thermal medium is opened when a load applied to the engine is low and the flow-path of the thermal medium is shut when the load applied to the engine is high.
Accordingly, when the amount of the fuel supplied into the combustion chamber is small and the temperature inside the combustion chamber is low on account of low load applied to the engine, the diesel engine can be warmed by circulating the heated thermal medium thereby enhancing ignition and complete combustion of the fuel. On the other hand, when the amount of the fuel supplied into the combustion chamber is great and the temperature inside the combustion chamber is high on account of high load applied to the engine, the flow-path of the thermal medium is shut to stop circulation of the thermal medium, thereby preventing the temperature of the diesel engine from being excessively raised by the thermal medium. Further, since the air density of the intake air is not lowered because the thermal medium does not heat the diesel engine, i.e. does not heat the intake air, the flow of the intake air supplied into the combustion chamber is not reduced and decrease in the output of the diesel engine can be avoided.
Further, the diesel engine may preferably include a plurality of combustion chambers, and the combustion stabilization assist may preferably have a function for stopping fuel supply to a part of combustion chamber of the plurality of combustion chambers.
According to the above arrangement, the fuel supply to the part of the combustion chamber is stopped by the combustion stabilization assist during the predetermined period. In this case, since the explosive force from the part of the combustion chamber cannot be obtained, the load applied to the diesel engine is increased. Then, the diesel engine increases the amount of the fuel supplied to the rest of the combustion chambers in response to the increase in the load, so that the temperature of the exhaust is raised to raise the temperature inside the combustion chamber, thereby enhancing ignition and complete combustion of the fuel.
Alternatively, the combustion stabilization assist may preferably have a function for advancing a timing for supplying fuel to the combustion chamber to be earlier than the a timing for supplying fuel during loaded operation mode of the diesel engine.
According to the above arrangement, the fuel supply timing to the combustion chamber is advanced by the combustion stabilization assist to be earlier than the fuel supply timing of the loaded operation mode of the diesel engine during the predetermined period.
Ordinarily, in a diesel engine, the fuel injection timing is controlled in accordance with engine speed, where retard timing control of the fuel supply timing is often conducted in the engine speed area of loaded operation mode (an operation mode working as a motor) of which operation time is long, in order to reduce NOx in compliance with exhaust gas restriction. In such loaded operation mode, since the amount of the fuel supplied into the combustion chamber is great and the inside of the combustion chamber is sufficiently warm, ignition and complete combustion of the fuel can be conducted well.
However, since the above retard timing control is conducted in accordance with the engine speed, when the rotation speed area of the loaded operation mode is approximately coincident with, for instance, the rotation speed during high-idle operation of the diesel engine, the retard timing control of the fuel supply timing is conducted in the neighborhood of the high-idle condition. Accordingly, the fuel supply timing is retarded even when the amount of the fuel supplied into the combustion chamber is small and the combustion chamber is not sufficiently warmed, so that ignition and complete combustion of the fuel may not be sufficiently conducted, thereby increasing the discharge of white smoke.
In the present arrangement, since the fuel supply timing into the combustion chamber is advanced to be earlier than the loaded operation mode of the diesel engine at least from the pre-idle step of the diesel engine to the neighborhood of the high-idle condition by the combustion stabilization assist, ignition and complete combustion of the fuel can be conducted well, thereby securely reducing discharge of white smoke.
In the above-described diesel engine, when fuel of inferior autoignition properties, such as emulsion fuel in which water and fuel is mixed in emulsion, waste plastic decomposition oil, methanol fuel etc. is used, since the ignition properties can be greatly enhanced, the present invention can be suitably applied.